With the development of multi-media systems, the prospect of capturing high quality video on a computer system has become desirable. However, capturing high quality video is difficult because video capture devices commonly utilize a low data rate interface, such as universal serial bus (USB) to send video data to a computer. A USB interface, for example, has a significantly smaller data rate than the actual video data rate and a much smaller data rate than required to capture high quality video.
Each frame of video generally takes the form of many thousands of pixels where each pixel can be represented by several bytes of data. For example, a conventional video frame may be comprised of 720×480 pixels and each pixel may be represented by three bytes. At a conventional rate of 30 frames per second and without the use of compression techniques, transmission of conventional video requires a data rate of at least 250 Mega bits per second (Mbps). At present, a USB interface can support a maximum data rate of about 12 Mbps of which only about 5-8 Mbps can be sustained. Conventional compression techniques used to compress video data prior to transmission over a USB interface result in poor quality video because the compression techniques result in a loss of data.
For example, one conventional method of reducing information in compressed video images is to discard higher frequency components of the video images. This technique works because the human vision system is not as sensitive to high frequency video components as it is to low frequency video components. While this technique does reduce the amount of information that is conveyed, the video images lose detail and may begin to look blurry. Another conventional method of reducing information in compressed video images involves quantizing the image parameters. Although this technique improves the encoding operation, images appear blocky because gradual changes may take on the appearance of stepped changes in the video image.
Thus there is a need for a method and apparatus that provides high quality video capture using a low data rate interface. There is also a need for a video capture device and method of sending high quality video over a low data rate interface. There is also a need for method of generating high quality video with information received over a low data rate interface. There is also a need for a method and video capture device for compressing and sending video over a USB interface to capture high quality video.
The description set out herein illustrates the various embodiments of the invention and such description is not intended to be construed as limiting in any manner.